1. Technical Field
Embodiments described herein relate to a wiring substrate and a method of manufacturing a wiring substrate.
2. Description of the Related Art
In the related art, a substrate on which electronic components are mounted is a so-called multi-layer wiring substrate in which a plurality of insulating layers and wiring layers are formed on both surfaces of a core substrate. The material of the core substrate is glass epoxy, for example. In such a wiring substrate, the difference in the thermal expansion coefficient between the wiring pattern (for example, copper) of the wiring layer and the core substrate causes warpage due to thermal expansion in the wiring substrate. The use of a material with a low thermal expansion coefficient, for example, glass, for the core substrate is one effective method to reduce the warpage of the wiring substrate (for example, see JP-A-2003-204152).
Meanwhile, according to an increase in the number of integrated elements and signal processing in electronic components (for example, semiconductor chips) in recent years, the density of wiring lines formed on the substrate partially increases with an increase in the number of electrode pads formed in the semiconductor chip (an increase in the number of pins). For this reason, it is not possible to form wiring lines on the wiring substrate having a predetermined number of layers.
On the other hand, a configuration may be considered in which the diameter of a through electrode connected to a semiconductor chip, among through electrodes formed in a core substrate, is partially reduced. However, when glass is used as the core substrate, it is difficult to form through electrodes having different diameters in the same core substrate.